I would like to use the site ilcorsaronero.info as a search engine for torrents.The links that return the search are not direct links to the .torrent files, but pages in which code there is a magnet link.Is it possible to configure flexget to extract that link?

When you submit a query, resulting page doesn't have any magnet or torrent links. You are getting list of links, which points to separate html pages. Different one for each entry. Links to magnets and torrents are on those separate pages.

In theory (if you are a developer or if you have someone to do it for you), you could make a intermediate page that would act as a mediator between that site and flexget. Another approach would be to add this to flexget directly, but that requires good python skills.

If your search returns for example 100 results, in order to retrive links, you need to send 101 request to that website insted of just one. 101 request just for one video file! But only if that is a movie. If it is a TV series, flex get would send few more requests for every episode. So for series, that number might be even 505 for first episode of some show. Now imagine that you are sercihg for 20 movies and 20 series. Congratulations, you just made yourself a perfect candidate for permanent ban, especially if you send those request too quickly.

To summarize - do not try this if you are not experienced developer. Even if you are, I would not advice to try to use this site with flexget. I advice to try to find some other source.